Core signal translating devices



March. 6, 1962 H. w. ABBOTT CORE SIGNAL TRANSLATING DEVICES Filed Aug. 6, 1958 FIG.2.

FIG.I.

CONTROL AC INPUT AC OUTPUT T U P U o c A FIG.4.

FIG.3.

MULTIPATH CORE UNBLOCKED AC INPUT UNBLOCK AC OUTPUT MULTIPATH CORE BLOCKED INVENTORI HAROLD w. ABBOTT, BY M4 ms ATTORNEY.

United States Patent 9 P 3,024,447 CQRE SIGNAL TRANSLATING DEVKCES Harold W. Abbott, Cohoes, N.Y., assignor to General Electric Company, a corporation of New York Filed Aug. 6, 1958, Ser. No. 753,537 9 Claims. (Cl. 340-174) This invention relates to core signal translating devices. More particularly, the invention relates to alternating current signal driving means for multi-path magnetic core devices which are commonly used in information handling systems.

Known multi-path magnetic core devices are described by J. A. Rajchman, and A. W. Lo in an article entitled The Transfluxor appearing at pages 32l332 of the Proceedings of the IRE of March 1956. Additional disclosures relating to multi-apertured magnetic devices are made in an application for US. patent entitled, Signal Translating Device, Serial No. 632,342, filed January 3, 1957, and now Patent No. 2,863,136 of which the inventor of the present application is one of the co-inventors, and which is assigned to the assignee of the present invention. The multipath core devices described in the above-referenced disclosures are selectively blocked and unblocked. When the core is in the blocked state an alternating current signal applied to an alternating current, i.e. A.-C., signal input winding will not be transferred to an A.-C. signal output winding, Whereas when the core is in the unblocked state, the alternating current signal which is applied to the A.-C. signal winding is coupled to the AC. signal output winding.

Proper operation of multi-path cores imposes constraints on the A.-C. driving circuits which supply the A.-C. input signal to the A.-C. signal input winding, and require special driving means for the A.-C. input driving signal. The driving circuit problems may be clarified by explanation of a representative multi-path core configuration. It should of course be understood that the present invention is not limited to any one core configuration. I

One of the earlier of such multi-path magnetic core devices comprises a three-legged core of magnetic material having a nearly rectangular hysteresis loop. The core has two circular apertures with unequal diameters arranged so that the material between each of the two apertures and the respective adjacent edge of the core forms first and third legs respectively, while the material between the two apertures themselves forms the second leg of the three-legged core. A control Winding is placed on the third leg bounding the larger aperture. Signal input and signal output windings are placed respectively, on the first and second legs. In operation, a current pulse sent through the control winding will saturate the two smaller legs, i.e. the first and second legs, in the same direction since the larger leg provides the necessary flux return path for the flux from both of the smaller legs. The core is then blocked because the remanent flux has the same direction, and is nearly equal to the saturation flux, in both the first and second legs bounding the small aperture. At least a part of the shortest magnetic circuit coupling the input and output windings is therefore already saturated with respect to either polarity of the A.-C. signal and no flux can be transferred to link the windings. To unblock the core and permit passage of a small alternating current signal from the input to the output winding, an unblocking pulse is applied to the control winding. When the core is unblocked a small applied A.-C. signal may be viewed as transferring flux back and forth between the first and second legs in a magnetic circuit surrounding the smaller aperture and a signal output may be derived.

3,024,447 Patented Mar. 6, 1962 Successful operation of multi-path cores, including the 'type above-described, imposes critical limitations on the A.-C. signal applied to the A.-C. signal input winding both when the multi-path core is blocked and unblocked. When the core is blocked, current in the A.-C. signal input winding must be limited to less than the coercive current value for the flux path around the first and third legs, i.e. the peripheral flux path, otherwise the saturation flux will change in this path and the core will be un blocked. When the core is unblocked, the signal input current must be larger than the coercive current value for the flux path around the first and second legs, i.e. the desired signal path, otherwise there will be no flux change in this path and no output will be obtained from the A.-C. signal output winding. Thus, when the core is blocked the peak current amplitude of the A.-C. input signal must be limited, while with the core unblocked, the volt-second characteristic must be suflicient to induce a secondary voltage.

It is insufiicient to merely employ a source with a serially connected impedance for limiting the A.-C. input signal to some value between the coercive value of the desired signal path and the coercive value for the peripheral path. Such an A.-C. signal input system is subject to the following disadvantages:

(1) The necessity for a current-source as the alternating current input leads to considerable signal waveform distortion because of the non-linearity of the square-loop characteristics of the core.

(2) Due to changes in the coercive magnetomotive force requirements of the various core paths as a consequence of temperature variations, the alternating current output signal becomes a function of temperatures. At low temperatures the coercive value may increase to the point where the A.-C. signal output falls the zero, while at high temperatures it may not be possible to block the core in view of the decrease of the coercive value for the peripheral, or undesired flux path below the peak value of the alternating current path.

(2) The effective alternating current input impedance of the AC. signal input winding varies considerably between the blocked and unblocked states of the multi-path core device and thus leads to severe driving source requirements, particularly when it is desired to drive several devices from a single alternating current source.

It is therefore an object of this invention to provide an alternating current input signal circuit for multi-path magnetic core devices which overcomes the above-described disadvantages of known devices and circuits.

It is a further object of this invention to provide such an A.-C. input circuit capable of operating from a voltage source.

It is a further object of this invention to reduce the driving power requirements of the A.-C. input signal.

It is a further object of this invention to increase the ratio of the A.-C. output voltage of the multi-path core between the unblocked and blocked states.

Briefly, in accordance with one aspect of the invention, the alternating current signal input winding means are connected in cooperative relationship with a separate driver core in addition to being wound about at least one leg of the multi-path means core. The driver core, which may be a toroidal core, limits the A.-C. input current and ofiers a relatively high constant impedance to the driver source when the multi-path core is in the blocked state and while it is in the unblocked state. The A.-C. input windingof the multi-path core may be wound about the additional core, which will be referred to as the driver core, so that the latter will be wound in parallel with the A.-C. input leg of the multi-path core, i.e. the first leg in the above-described example. Alternatively, a separate winding placed about the driver core may be placed in series with the A.-C. signal input winding of the multi-path core. Where the driver core is wound in parallel with the multi-path core the path length of the driver core is selected so that the value of coercive ampere turns falls between the coercive ampere turn value for the multi-path core desired signal flux path and the undesired, i.e. peripheral signal path. Whereas, when a separate driver core winding is placed in series with the A.-C. signal input winding of the multi-path core, the coercive ampere-turns of the driver core may be directly adjusted. By proper design of the driver core, a voltage source may be used as the A.-C. input signal source. If a voltage source is applied to the A.-C. signal input and the multi-path core is blocked, the input current will be limited by the coercive value of the driver core, to a lower magnitude of current than the coercive value of the peripheral leg, so that the multi-path core cannot be unblocked by the input signal. It the multipath core is unblocked, the input current will be limited by the coercive current magnitude for the desired signal path. The flux in the desired signal path will then be varied in accordance with the input signal so that an output will be obtained from the A.-C. signal output winding. In addition to limiting the magnitude of the A.-C. input signal, the driver core permits the A.-C. driving circuit to appear as a continuous high impedance. If the driver core is made of the same material as the multi-path core, the coercive value of the driver core Will vary with the coercive value of the multi-path core flux paths with temperature change so that automatic temperature compensation will result.

While the novel and distinctive features of the invention are particularly pointed out in the appended claims, a more expository treatment of the invention, in principle and detail, together with additional objects and advantages thereof, is afforded by the following description and accompanying drawings of representative embodiments in which:

FIG. 1 is a schematic plan view of a two-hole core driving circuit employing a driver core wound in parallel with the A.-C. input leg of the two-hole core.

FIG. 2 is a schematic plan view of a two-hole core driving circuit having a driver core winding placed in series with the A.-C. signal input winding of the twohole core.

FIG. 3 is a schematic plan view of a four-hole core driving circuit having a driving core wound in parallel with A.-C. input leg of the four-hole core.

FIG. 4 is a plot of typical hysteresis characteristics of the alternating current input winding terminals of a multipath core and the characteristics of the driver core when the multi-path core is in the unblocked state.

FIG. 5 is a plot of typical hysteresis characteristics for a multi-path core similar to those of FIG. 4, but for a blocked multi-path core.

Turning now to the drawings, and in particular to FIG. 1, there shown is a conventional two-hole core, such as disclosed in the previously referenced article, which, additionally includes the applicants novel driving circuit. It should be noted that the applicants invention is applicable to a variety of multi-aperture core devices, and may thus be utilized with a four-hole core configuration as illustrated in FIG. 3, as well as being utilized with a variety of other multi-path core configurations. The core is formed of a magnetic material having a substantially rectangular hysteresis characteristic and may be manufactured of a molded ferrite ceramic, or possibly of other material, ferrite or otherwise, having the abovenoted substantially rectangular magnetic hysteresis characteristics. The core is provided with two circular apertures of unequal diameter, B and A, arranged so that the material between each of the two apertures and a respective adjacent edge of the core forms first and third legs, respectively, while the material between the two apertures themselves forms the second leg of the three-legged core. Thus, leg 3 is adjacent to large aperture A, peripheral leg 1 is adjacent to small aperture B and intermediate leg 2 is between the two apertures. The control winding 4 is wound about leg 3, which has a minimum cross-sectional area equal to the sum of the smallest cross-section areas of the other two legs. Alternating current signal input and output windings are wound on the core legs surrounding aperture B, with A.-C. signal output winding 5 wound about core leg 2 and signal input winding 6 being wound about peripheral core leg 1. Applicants invention resides in the driving circuit of the A.-C. signal input winding. It may thus be seen that signal input winding 6 is wound about both driver core 20 and peripheral leg 1 of core 10. Winding 6 is connected to an A.-C. signal source 7, which is preferably a voltage source. The driver core illustrated in FIG. 1 may be a single aperture core having a path length which is critically related to the flux paths of core 10.

FIG. 3 illustrates a four-hole core configuration, as disclosed in the previously referenced application for US. patent, with an A.-C. drive circuit of the type discussed above. Core 30 is provided with four separate but mutually contiguous apertures, C, D, E, and P, which are placed so that the material between any one pair of apertures forms one of five interior legs 11 through 15, while the other four legs, 16 through 19, are formed by the material between each of the apertures and the edge of peripheral core. As is described in more detail in the above-referenced application for US. patent, the control, or block, winding 21 is wound on the first peripheral leg 16, and unblocking windings 22 and 23 are wound, respectively, on peripheral legs 19 and 17. An A.-C. signal output winding 24 is shown wound about interior core leg 11 which adjoins the four apertures. The output winding may, of course, be instead wound about core leg 18. The alternating current signal input winding 25 is wound about the peripheral core leg 18 and also driver core 20, and has its output connected to A.-C. signal source 7, which is preferably a voltage source.

The operation of the applicants novel A.-C. input signal drive circuit is described in respect to the two-hole core of FIG. 1. Operation of the two-hole core device of FIG. 1 is dependent upon the saturation flux states in legs 1 and 2, so that when these states have the same sign, the transfluxor is blocked and ideally no A.-C. signal transfer can occur between legs 1 and 2. However, if a pulse of sufficient energy is applied to the control winding so that the saturation flux state of leg 2 is reversed without the flux state of leg 1 being altered, the multihole core is unblocked. In the unblocked condition, flux changes in the closed magnetic path 1-2 may occur and hence an A.-C. signal is readily transferred from the AC. signal input to the A.-C. signal output terminals. Thus in order to block the core the control winding current must exceed the coercive value of current for the flux path 13, while in order to unblock the core, the control pulse current amplitude must be less than the coercive current value for the flux path of legs 1 and 3, but greater than the coercive current value of the flux path through legs 2 and 3. As previously stated, successful operation of the core device does not only require a proper control pulse input, but is additionally dependent upon the requirements of the alternating current input signal. The requirements imposed upon the A.-C. signal input neglecting the driver core are:

where the I is the peak magnitude of the applied A.-C. current, I is the magnitude of current which will establish the coercive magnetomotive force of the closed path 1--2, and I is the magnitude of current which will establish the coercive magnetomotive force of the closed path through legs 1 and 3. This equation indicates that the A.-C. signal input current must be large enough to ensure flux changes in the magnetic path 12, but must be small enough to prevent substantial flux changes in the path 1-3. These conditions are required, as has been previously stated, because when the core is blocked, the current in the input winding must be limited to less than the coercive value for the path around legs 1 and 3 so that there will be no flux change in this path to unblock the core. If the core is unblocked, the input current must be larger than the coercive value for the flux path in legs 1 and 2, otherwise there will be no flux change in this path and no output will be obtained from the winding on leg 2. Further, an additional requirement imposed upon the A.-C. signal input, again neglecting the driver core, is:

where f is the frequency of the A.-C. input signal, E is the peak magnitude of the A.-C. voltage, and is the saturation flux corresponding to the path 1-2, and N is the number of turns around leg 1. The inequality given by the preceding equation is established by the requirement that the A.-C. input signal should not exceed the volt-second limit which would cause complete reversal of the saturation flux state in the path 12. The saturation flux values and the coercive magnetomotive force values of the multi-path core are determined by the geometry of the core.

The above-stated requirements are met, and the initially stated disadvantages of current limited A.-C. input signals are overcome, by providing a driver core 20, in the A.-C. signal input circuit. In the modifications illustrated in FIGS. 1 and 3, this core is wound in parallel with the A.-C. input leg of the multi-aperture core, legs 1 and 18, respectively.

The design requirements of the driver core are illus trated by the hysteresis curves of FIGS. 4 and 5, which are applicable alike to the twoand four-hole configurations illustrated in FIGS. 1 and 3. The closed magnetic paths of either of the multi-aperture cores, referenced in respect to the A.-C. signal input legs, 1 and 18 respectively, are denoted by the subscripts G and H. G is the desired signal path and H is the peripheral path. The closed path of the driver core is denoted by the subscript K. In respect to the two-hole core configuration of FIG. 1 it may be seen that the desired signal path G traverses core legs 1 and 2, while the peripheral path H traverses core legs 1 and 3. In the four-hole core configuration of FIG. 3, it may be seen that the desired signal path G traverses core legs 11, 13, 18, and 14, while the peripheral path H traverses core legs 18, 19, 16, and 17.

The coercive requirement ofthe driver core 20 is given by the following:

(3) states that the coercive magnetomotive force of the driver core should have a magnitude which lies between the coercive requirements of the multiple core paths G and H. Thus, in the modification of FIGS. 1 and 3 the elfective length of the flux path of the driver core is greater than the length of path G but less than the length of path H of the multi-aperture core if both the multiaperture core and the driver core are fabricated from the same material and if the turns linking both are the same.

The requirements imposed upon the A.-C. signal source are:

where I is the current required for reaching the coercive M.M.F. of the driver core and is the saturation flux density of the driver core. It is noted from (4) and (5) that the A.-C. signal requirements are new independent of the multi-path core.

By requiring that the A.-C. signal should never fully reverse the saturation state of the driver core, as given by (5), the peak value of A.-C. magnetizing current applied to the multi-path core can never exceed the coercive current of the driver core. As a consequence of (3), therefore, the multi-path core can never be unblocked by the AC. signal. Furthermore, if the multipath core and driver core are made from the same ferrite materials, the temperature effects upon the magnetic properties of both will be the same and automatic temperature compensation will occur.

An additional advantage of the driver-core input technique is that the mu lti-path core is driven from a voltage source and hence, a truer waveform is induced in the A.-C. output winding. Since current is no longer limited by the generator, the A.-C. output winding may be more heavily loaded. When the multi-path core is blocked, the impedance of the A.-C. driving terminals remains substantially the same as when the multi-path core is unblocked, since the NI excursion is now controlled by the driver core. Hence, all of the disadvantages of an A.-C. current source are overcome by using the driving core technique, while all the advantages associated with the use of a current source are maintained.

In one particular application of the embodiment illustrated in FIG. 3; the four-hole core diameter the distance between the centers of apertures E and C= the distance between the centers of apertures D and F the diameter of apertures E and C and the diameter of apertures D and F The associated driver core outside diameter the inside diameter 4". Employing an arbitrary A.-C. signal frequency of 20 kc. and an input voltage of about /2 volt, it was found that the output voltage was substantially constant over a temperature range from about -40 C. to +200 C. It was also noted that a substantial increase in the ratio between the unblocked to blocked A.-C. output voltage was obtained, for this entire temperature range, in respect to a current driven resistance limited circuit. The values stated above are listed only for purpose of explanation and do not, of course, constitute critical limitations.

The embodiment of FIG. 2 is akin to that of FIG. 1 except that the A.-C. signal input winding 8, which is wound about leg 1 of core 10, is serially connected to winding 9, which is independently wound about a leg of driver core 20. The design requirements follow those of Equations 3 through 5.

Although the A.-C. driving circuits have, for convenience and clarity of illustration been shown, in respect to twoand four-hole cores, it will of course be understood that such circuits may similarly be employed with multipath cores of other configurations.

While the principles of the invention have now been made clear in illustrative embodiments, there will be immediately obvious to those skilled in the art many modifi cations in structure, arrangement, proportions, the elements and components, used in the practice of the invention and, otherwise, which are particularly adapted for specific environment and operating requirements without departing from those principles. The appended claims are therefore intended to cover and embrace such modifications, within the limits only of the true spirit and scope of the invention.

What I claim as new and desire by Letters Patent of the United States is:

1. A core sign-a1 translating device comprising, a first magnetic circuit comprising a multi-path core having alternating current signal winding means thereon, said first magnetic circuit having a substantially rectangular hysteresis curve characteristic, a second magnetic circuit comprising a driver core having alternating current signal winding means thereon, said second magnetic circuit having a substantially rectangular hysteresis curve characteristic, input terminals for connection to a voltage signal source, said driver core having magnetic characteristics so that the alternating current input impedance is substantially the same when said multi-path core is blocked as when said multi-path core is unblocked, and means connecting the alternating current signal winding means of said multi-path core and the alternating current signal winding means of said driver core to said input terminals.

2. A core signal translating device comprising a first magnetic circuit comprising a multi-path core constructed of a material exhibiting a substantially rectangular hysteresis curve characteristic and having alternating current input signal winding means thereon, said core having a first and a second flux path common to said winding means, said second path requiring a coercive magnetomotive force greater than that of the first path, input terminals for connection to an alternating current signal source, a second magnetic circuit comprising a driver core constructed of a material exhibiting a substantially rectangular hysteresis curve characteristic and having a driver winding means thereon, said second magnetic circuit requiring a coercive magnetomotive force intermediate to that required by said first and second paths, and means connecting said driver winding means in electric circuit with said alternating current signal winding means to said input terminals for limiting the energization of said alternating current signal winding when signals are applied thereto to a value below that required for providing a coercive magnetomotive force in said second path whereby flux changes may be produced in said first path but not in said second path.

3. A core signal translating device as in claim 2 wherein the alternating current signal source is a voltage source.

4. A core signal translating device as in claim 2 wherein the multi-path core and the driver core are fabricated of the same material.

5. A core signal translating device comprising a multipath core constructed of a material exhibiting a substantially rectangular hysteresis curve characteristic and having alternating current signal winding means thereon, said core having a first and a second fiux path common to said winding, said second path requiring a coercive magnetomotive force greater than that of the first path, a driver core constructed of a material exhibiting a substantially rectangular hysteresis curve characteristic and requiring a coercive magnetomotive force intermediate to that required by said first and second paths, said alternating current signal winding means coupled to the first and second paths of said multi-path core and to said driver core for limiting the energization of said alternating current signal winding when an alternating current signal source is applied to said winding means to a value below that required for providing a coercive magnetornotive force in said second path, so that flux changes may be produced in said first path but not in said second path.

6. The device of claim 5 wherein the driver core length is intermediate to the lengths of said first and second paths.

7. The device of claim 5 in which the alternating current signal source is a voltage source having a frequency greater than where E is the maximum voltage amplitude of the signal source, N is the number of turns of said A.-C. signal winding means and is the saturation flux density of the driver core, and where said source is capable of providing a current amplitude in excess of that required for reaching the coercive magnetomotive force of the driver core.

8. A core signal translating device as in claim 5 in which the alternating signal source is a voltage source having a frequency greater than 1!) 1s1'2 where E is the maximum voltage amplitude of the signal source, N is the number of turns of said alternating current signal winding means and is the saturation flux density of said first path, whereby the saturation state of the flux in said first path is prevented from being completely reversed.

9. A core signal translating device comprising a multipath core constructed of a material exhibiting a substantially rectangular hysteresis curve characteristic and having an alternating current signal winding means wound thereon, said core having a first and a second fiux path common to said alternating current signal winding means, said second path requiring a coercive magnetomotive force greater than that of the first path, input terminals for connection to an alternating current signal source, a magnetic circuit comprising a driver core constructed of a material exhibiting a substantially rectangular hysteresis curve characteristic and having driver winding means thereon, said magnetic circuit requiring a coercive magnetomotive force intermediate to that required by said first and second paths, and means for serially connecting said alternating current signal winding means and said driver winding means to said input terminals for limiting the energization of said alternating current signal winding when signals are applied thereto to a value below that required for providing a coercive magnetomotive force in said second path, so that flux changes may be produced in said first path but not in said second path.

References Cited in the file of this patent UNITED STATES PATENTS 2,272,998 Bjornson Feb. 10, 1942 2,375,609 Zuhlke May 8, 1945 2,566,974 Bastian Sept. 4, 1951 2,708,219 Carver May 10, 1955 2,863,136 Abbott et a1. Dec. 2, 1958 2,882,482 Simkins Apr. 14, 1959 OTHER REFERENCES Proceedings of the IRE, vol. 44, issue 3, pp. 321-332, March 1956, The Transfluxor by Rajchman et al.

Proceedings of the IRE, pages 10811093, Multihole Ferrite Core Configurations and Applications, Aug. 9, 1957 by Abbott et a1. 

